在光学领域，任何光学仪器或系统，无论是显微镜、望远镜还是相机，由于衍射的物理特性，其分辨率都有一个主要极限。
In optics, any optical instrument or system – a microscope, telescope, or camera – has a principal limit to its resolution due to the physics of diffraction.
如果光学仪器的分辨率性能达到了这一极限，则称其为衍射极限。
An optical instrument is said to be diffraction-limited if it has reached this limit of resolution performance.
其他因素也可能影响光学系统的性能，例如透镜缺陷或像差，但这些是由透镜制造或计算中的误差引起的，而衍射极限是理论上完美或理想的光学系统所能达到的最大分辨率。
Other factors may affect an optical system's performance, such as lens imperfections or aberrations, but these are caused by errors in the manufacture or calculation of a lens, whereas the diffraction limit is the maximum resolution possible for a theoretically perfect, or ideal, optical system.
仪器的 衍射极限角分辨率 （以弧度为单位）与 被观测光的波长 成正比，与 物镜入射孔径 成反比。
The diffraction-limited angular resolution , in radians, of an instrument is proportional to the wavelength of the light being observed, and inversely proportional to the diameter of its objective's entrance aperture .
对于具有圆形孔径的望远镜，图像中受衍射极限影响的 最小特征的大小 等于艾里斑（Airy disk）的大小。
For telescopes with circular apertures, the size of the smallest feature in an image that is diffraction limited is the size of the Airy disk.
随着望远镜头孔径的减小，衍射会成比例增加。在小孔径（例如f/22）下，大多数现代镜头仅受衍射限制，而不会受到像差或其他结构缺陷的限制。
As one decreases the size of the aperture of a telescopic lens, diffraction proportionately increases.As one decreases the size of the aperture of a telescopic lens, diffraction proportionately increases.
对于显微仪器，衍射极限空间分辨率与光波长成正比，并且与物镜或物体照明源的 数值孔径（以较小者为准）。
For microscopic instruments, the diffraction-limited spatial resolution is proportional to the light wavelength, and to the numerical aperture of either the objective or the object illumination source, whichever is smaller.
在天文学中，衍射极限观测是指在所用仪器尺寸范围内达到理论理想物镜分辨率的观测。
In astronomy, a diffraction-limited observation is one that achieves the resolution of a theoretically ideal objective in the size of instrument used.
然而，由于大气效应，大多数地球观测的视场都有限。
However, most observations from Earth are seeing-limited due to atmospheric effects.
由于光线穿过数公里湍流大气时产生的畸变，地球上的光学望远镜的分辨率远低于衍射极限。
Optical telescopes on the Earth work at a much lower resolution than the diffraction limit because of the distortion introduced by the passage of light through several kilometres of turbulent atmosphere.
先进的天文台已经开始使用自适应光学技术，从而提高了暗淡目标的图像分辨率，但使用自适应光学技术仍然难以达到衍射极限。
Advanced observatories have started using adaptive optics technology, resulting in greater image resolution for faint targets, but it is still difficult to reach the diffraction limit using adaptive optics.
射电望远镜通常受到衍射极限的影响，因为它们使用的波长（从毫米到米）非常长，大气畸变可以忽略不计。
Radio telescopes are frequently diffraction-limited, because the wavelengths they use (from millimeters to meters) are so long that the atmospheric distortion is negligible.
太空望远镜（例如哈勃望远镜或许多非光学望远镜）如果其设计没有光学像差，则始终工作在衍射极限。
Space-based telescopes (such as Hubble, or a number of non-optical telescopes) always work at their diffraction limit, if their design is free of optical aberration.
具有近乎理想光束传播特性的激光器产生的光束可以被描述为衍射极限光束。
The beam from a laser with near-ideal beam propagation properties may be described as being diffraction-limited.
衍射极限激光束穿过衍射极限光学元件后，仍将保持衍射极限，其空间或角度范围基本等于光学元件在激光波长下的分辨率。
A diffraction-limited laser beam, passed through diffraction-limited optics, will remain diffraction-limited, and will have a spatial or angular extent essentially equal to the resolution of the optics at the wavelength of the laser.
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